Packaging machines are known that integrate the various components necessary to fill and seal a container into a single machine unit. The process of packaging, generally stated, includes feeding carton blanks into the machine, sealing the bottom of the cartons, filling the cartons with a desired volume of product, sealing the top of the cartons, and then off loading the filled cartons from the machine for subsequent distribution.
The operation of the various components used to form, fill, and seal the cartons must be coordinated so that the desired function is carried out on the carton at the desire time. Known systems coordinate the movement of the various components using a main drive shaft common to the various components. Employing a common drive shaft ensures that the various components of the machine execute coordinated movements whereby specific functions executed by one component are carried out at an appropriate time with respect to the other functions executed by other components.
One example of a machine utilizing a common drive shaft is disclosed in U.S. Pat. No. 3,820,303 to Martensson et. al. The common drive shaft of the machine disclosed in the '303 patent is located below the table of the machine, and includes a variety of cams and other actuating means, such as gear boxes, that provide appropriate movement to the various machine components.
As will be appreciated, precise control of the filling system is necessary in order to assure that each container receives the desired quantity of product. In practice, such precision can be difficult to achieve. Typically, the product filling system is cam-operated, and is ordinarily mechanically linked to the common drive shaft that drives the associated container conveyor. Cam operation of the product pump of this type of system has been found to desirably provide superior volume control, when compared to pneumatic systems, and desirably consistent operation of the pump devices. This type of system desirably avoids problems associated with fluctuations in product supply pressure and air supply pressure, and imprecise operator control.
Despite certain advantages, such cam-operated systems lack versatility, since the system typically performs optimally within a limited speed range, and thus does not lend itself to running at higher or lower speeds. When the system is run at other than its optimal speed, undesirably high product reject rates result. Additionally, such systems do not readily lend themselves to changes in product volume. Each cam which is driven by the common drive shaft is only capable of driving the pumping piston through a single range of motion, resulting in delivery of a single volume of product.
The volume delivered may be altered by changing the profile of the cam used to drive the pumping piston. Systems are known which provide multiple cam profiles. These systems involve at least two limitations. First, the range of output volumes available to the machine user are limited by the availability of cam profiles. For example, if cam profiles are available for 1/2 pint and 1 pint volumes, the user would be unable to fill cartons of 3/4 pint without ordering or machining a new cam profile. Second, even if the user has the appropriate cam profile available, the system must be shut down, and the appropriate cam profile must be manually changed to engage the appropriate cam follower.
Other systems are known where a horizontal piston rod is driven by a servomotor with a linear, screw-type actuator. This system provides a variable piston stroke that is controlled by a servomotor control system. These systems, however, include the bulk of their moving components above the cartons to be filled. They thus create the potential for contamination. Additionally, these systems are incapable of being retrofit to replace the cam structures typically used on existing machines.